Steam aerosol



United States Patent 3,316,056 STEAM AEROSOL Robert L. Johnson and William D. MacRae, Midland, Mich., assignors to The Dow Chemical Company, Mid land, Mich., a corporation of Delaware No Drawing. Filed May 8, 1963, Ser. No. 278,995 3 Claims. (CI. 21-57) The present invention is concerned with the preservation of water-insoluble fibrous substances such as wood, rope, cellulosic fabrics and fibers, leather, and the like, and is particularly directed to the application to such fibrous susbtances of a residual pesticidal preservative substance by a novel steam aerosol technique.

Many techniques for the distribution of pest controlling substances are known. One widely used technique is the production of a cold fog, that is to say a fog at ambient temperatures, which is then distributed around and over an article upon the surface of which it is desired to achieve distribution of a pesticide. This method has been applied with excellent results to, for example, large trees whereof it is desired to apply a pesticide to the whole exterior surface.

Steam distillation of volatile materials has also been employed as a distribution technique. In a steam distillation technique, a pest-controlling substance volatile at the temperature of steam is introduced into a moving current of steam and, at such temperature becomes a vapor of the pest-controlling susbtance, being carried with the current of steam and vapor droplets resulting from condensation of the steam until such time and place as it cools to a condensation temperature, whereat it condenses perhaps first to the liquid and subsequently perhaps, depending upon its properties, to the solid phase.

Such steam distillation techniques are sometimes modified by introduction of the pest controlling substance into the current ofsteam in the form of a solvent solution thereof. In such technique, commonly the solvent is flashed or azeotroped away, leaving in the steam separated vapors of solvent and of an essentially solvent-free pesticide substance.

Each of these techniques has serious disadvantages. In the case of the application of a cold fog, excellent results are obtained when application is made to an essentially wholly exposed structure such as the surfaces of a tree, or a Wholly exposed flat surface or geometric assembly of flat surfaces such as a building interior. However, when it becomes necessary to introduce the pesticide agent into the depth of a material characterized by organization or compaction into a body with relatively small pores or interstitial spaces, the particles of cold fog tend to coalesce and form surface droplets which then spread over or fall from surfaces in the familiar run-olf phenomenon, with very poor interstitial penetration.

The use of steam distillation is handicapped when it is desired that the pesticide achieve penetration into, rather than only surface application to, the said fibrous material. For example, cellulose and fibrous substances composed of it are notoriously excellent thermal insulators. It is impractical to heat the interior of a mass of cellulosic substance high enough to maintain the melting or vapor temperature of most ordinary organic compounds for a depth greater than that of a very shallow surface layer. Heating hot enough and long enough to admit of general distribution and penetration of a pesticide, by the steam heating alone, usually contributes to the thermal decomposition and steam hydrolysis of the cellulosic material in a manner destructive of its substance. Thus the characteristic results of the steam distillation application of a volatile solid pesticide is that a deposit of crystals of a frost-like nature forms on the surface of the fibrous sub- 3,316,056 Patented Apr. 25, 1967 stance but penetration beneath the surface is negligible.

It is an object of the present invention to achieve uniform distribution as a steam aerosol of a residual pesticide. It is a further object of the present invention to achieve a steam aerosol distribution of a residual pesticide with the result that the pesticide penetrates a treated water-insoluble fibrous material to a pesticidally significant depth. These, and other objects of the present invention which will become apparent from the specification and claims hereinafter, are achieved by the novel process which comprises introducing into a current of steam a readily flowable emulsifiable pesticide whereby a pesticide steam aerosol is produced and thereafter so directing the aerosol upon a water-insoluble fibrous material susceptible of pest attack that the aerosol reaches the fibrous material at a temperature at least about that of steam.

The flowable, emulsifiable pesticide is composed essentially of a pesticidal toxicant and an emulsifying agent. Knowing from the present specification the general nature of the present process those skilled in the arts of pesticide formulation will prefer an emulsifying agent that is characterized in the following way:

(1) It is essentially chemically stable and unreactive alone or with the employed pesticide at temperatures from approximately room temperature to the temperature of the employed steam,

(2) It is not wholly volatile in steam at the employed temperature,

(3) It forms a liquid colloidal emulsion of the pesticide in water.

The flowable, emulsifiable pesticide can contain, in addition to pesticide and emulsifying agent, one or more liquid pesticide adjuvants such as an organic solvent for all components, water, and the like.

More particularly, we have discovered the technique of distributing upon, with penetration into, a waterinsoluble fibrous substance susceptible of degradation through the vital processes of a living organism, of an organic residual pesticidal substance soluble, together with emulsifying agent, in an organic solvent, which comprises the steps of:

Preparing a solution of pesticidal organic substance and of emulsifying agent together in organic solvent,

Introducing the resulting solution into a flowing current of steam at such rate that the said steam substantially wholly entrains the said solution,

Conveying the resulting steam to a locus to be treated, Releasing the said steam near to the locus to be treated.

The said emulsifying agent being characterized by being:

(a) Essentially unreacted alone or with pesticide at a temperature from approximately room temperature to approximately steam temperature,

(b) Not wholly volatile in steam at the employed temperature, and

(c) Forming a liquid colloidal emulsion of the pesticide when cosolutions thereof with said pesticide are dispersed in water.

As is discussed hereinafter, our preferred embodiment is that wherein the locus to be treated is within a confining structure. Moreover, we regard as the best allpurpose pesticide for use in our process, insofar as we now know, to be a halo phenol.

When desired all components of the emulsifiable composition can be so selected that when material such as wood has been treated and thereafter allowed to become air-dry, it can safely be painted. Paint-compatibility of such substances has been well studied and known criteria can be applied.

The present method achieves distribution and penetration of various pesticidal substances to the site of and into the substance of fibrous materials. Whereas it has hitherto been possible by vapor and aerosol distribution to affect primarily only exposed surfaces, the present process, for reasons not fully understood, makes possible the distribution of a pesticide-bearing steam aerosol through narrow, tortuous and even labyrinthine passages of interstitial spaces and into relatively dense substances. One such situation is represented by a pile of lumber stacked in the manner usually employed for air drying of lumber, that is to say, with stickers (narrow spacers) between the layers of lumber to hold the lumber in layers spaced apart from one another, leaving interspaces of the same order of size as the smallest dimension of the lumber itself. Effective preservative treatment of such lumber has been quite impractical with the application of cold fogs. The fog tends to condense or coalesce on, or its movement to be deflected by, surfaces first contacted, and never thoroughly to reach the deeper interstitial spaces. However, by the present process, the steam aerosol penetrates thoroughly and conveniently into the lumber thus stacked, achieving excellent ingress and distribution through the interstices.

Also, whereas the methods of the prior art have resulted in heavy deposit of dry, typically crystalline pesticide upon treated surfaces, the present method achieves pesticidally significant penetration.

In the present invention, pesticidally significant penetration is used to mean essentially uniform interstitial ingress, and, therefrom, substantive penetration of the fibrous material (such as wood) to a consistent depth of at least a millimeter by such amount, relative to amount of material treated, of pesticide as is pesticidally effective against about 90 percent of a statistically significant pest sample by which the treated material is challenged.

Such penetration affords the treated substance protection by the employed pesticide when abrasion or minor surface injury removes the original surface. When pesticidal treatment is confined strictly to a surface, such minor injuries as can easily occur in handling lumber and the like greatly diminish its efiicacy; but even moderate surface penetration greatly diminishes the difficulties thus presented.

It will usually be desired and for the best application is critical that the process of the present invention be carried out under a cover which has the effect of at least directing the movement of, or loosely confining steam and water vapors. This cover may be of a temporary nature such as a cover of sheet metal, plastic, tarpaulin, or fabric, or may be permanent as in the form of a building, cavity in or partly in earth, or railroad box car. It need not be hermetically tight nor need it confine superatmospheric steam pressure.

In practicing the present invention, the substance to be treated will usually preferably be disposed in some manner to afford at least small but significant interstitial access routes to the surfaces to and through which treatment is to be applied, and will thereafter be exposed, usually under a confining cover, to the steam aerosol which is produced by introducing into a steam line an emulsifiable preparation comprising a pesticide which, depending upon its nature, may be combined with one or more liquid adjuvants and an emulsifying agent of the sort hereinbefore described, and thereafter causing the steam having the said pesticidal agent therewith to issue into the confined space and with access to the interstitial access routes to the surfaces to be treated.

Among the applications of the present invention which are comprised within the best mode of its practice presently contemplated are the treating of monolayer wooden structures such as wooden cooling towers for the evaporative cooling of liquids, lumber so stacked that it has no large occluded surfaces, incomplete frame structures such as houses of which the framing is exposed, wooden articles of manufacture and the like. Further, in the best method of practicing the present invention, the pesticidal substance to be dispersed as a steam aerosol can and advantageously should contain an anti-blooming agent. Blooming is the phenomenon of occurrence or distribution on the surface of a substance of some material which has migrated to the said surface from an earlier position within the depths of the material. In the instance of, for example, wood treated with a chemical agent, blooming is the appearance of the chemical treating agent on the surface of the wood as a result of its migration to the surface from an earlier position in the depths of the wood. Anti-blooming agents are agents which in any way retain or appreciably assist in retaining the chemical substance within the depth of the material preventing or inhibiting its migration out. The exact identity of an anti-blooming agent is not critical and will depend to some extent upon the identity and nature of the chemical substance of which it is to prevent blooming; most anti-blooming agents are chemically relatively simple and industrially well-known substances, such as alcohols, glycols, polyglycols and like substances having essentially hydrocarbon structures upon which appear oxygenated or other substituted structures of simple nature. Known anti-blooming agents function well in the present invention and any of them can be selected for desirable properties in a given application.

Either a water-soluble or a water-insoluble pesticide can be distributed effectively in the manner of the present invention. Whenever exposure of the treated entity to weather or moving water is a factor, a water-insoluble pesticide obtains the best results. To the extent that it is water-insoluble, a pesticide is proof against leaching out of the wood under the influence of flowing water including rain and the like. Because the present system does not rely upon water solubility for distribution of the substance employed, insoluble substances are readily distributed hereby.

The emulsifying agents to be employed may be any of a wide variety. As is well known in the emulsifying agent art, a commercial emulsifier is seldom manufactured to exact chemical identity, but is more often manufactured according to general chemical procedures so controlled as to obtain products with relatively uniform and reliable emulsifying properties. Thus, in practicing the present invention, it is not necessary that an emulsifying agent be employed upon the basis of any particular exact chemical identity or structure. Rather, it is necessary that the criteria hereinbefore set forth be met. These have been met advantageously in practice by the employment, as agent to emulsify the pesticide employed according to the present invention and effect its steam-aerosol distribution usefully, of any of several commercial emulsifying agents that are a blend of a sulfonate and a nonionic surfactant material More particularly, the sulfonate material employed with good result can be a product obtained from a mixed petroleum fraction of light color sulfonated by treating it with sulfuric acid and thereafter neutralizing with caustic (essentially sodium hydroxide) to obtain an ionic sulfonate. The non-ionic component can be essentially the product of reaction of a fatty acid with a substantial excess of ethylene oxide to obtain a polymeric structure whereof the fatty acid moiety provides the necessary hydrophobe portion and the ethylene oxide reaction product moiety affords the hydrophile portion. Total molecular Weight achieved by ethylene oxide reaction is controlled by periodic analysis of resulting product for emulsifying property based upon the relationship between the molar proportion of ethylene oxide moieties and the mean or average length of the fatty acid chains.

A blend of the two said substances, employed as emulsifying agent in the present invention, gives very satisfactory results. However, other emulsifying agents otherwise meeting the criteria hereinbefore set forth are used with good results.

The quantity, concentration, or proportion of pesticide to be employed is not critical, so long as the total amount employed be at least sufficient to achieve treatment of the desired area with penetration to the desired depth and concentration into the surface of the-substance being treated. When pesticide is employed at a lower concentration or relative proportion, injection of a relatively large amount into a steam current and resulting steam aerosol distribution can take place over a relatively longer period of time. Of course, the amount introduced into the steam line per unit time should be no greater than the steam current can entrain. This amount will depend upon such factors as steam pressure, velocity, diameter of the member through which the steam current is being conveyed, steam temperature, internal turbulence of the steam, distance and correlative cooling between the site of introduction of the pesticide and the point whereat the pesticide-bearing steam issues into the air, and so forth. However, by the simple expedient of providing means such as a valve whereby the rate of introduction of pesticide into the steam current can be controlled, those skilled in the art will entertain no difficulty in adjusting the rate of introduction of pesticide to a rate at which the steam current can entrain and as an aerosol distribute the said pesticide. Whether steam entrainment of the emulsifiable pesticide is complete is readily checked by, sampling and analysis of steam, checking steam line drains for retained, unfractionated pesticide, or visually checking the fluid moving in a steam line through a transparent tubular section.

However, in practice, no significant problem exists. Steam readily entrains and distributes as aerosol, pesticide formulations for use herein in amounts of from, as a lower limit maximum one part of pesticide formation to ten thousand parts steam, all parts by weight, up to a practical maximum under working conditions, one thou sand parts of pesticide formulation to ten thousand parts of steam, all parts by weight. This is a capacity and range so great as to make effective practice easy to carry out.

Conveniently, pesticide can be taken into the steam line by pickup through a Vcnturi or modified Pitot tube. Readily entrained amounts are thus conveniently introduced into the steam line.

The present technique does not depend upon steam, that is to say, thermal, sterilization of the surface or substance to be treated with pesticide. Rather, the aerosol distribution of the pesticide itself is the principal action upon which depends the process of the present invention. Non-pesticide substances otherwise meeting the criteria for employment in the present invention are also similarly distributed when treated according to the present invention.

The present invention has upon several occasions been practiced with good results.

' Upon a representative occasion, when the best known embodiment of the present invention was carried out, treatment was applied to a wooden industrial cooling tower, normally used for the cooling of hot aqueous industrial liquids at a petroleum processing plant. The cooling tower cell treated was 1 of 13 all alike. Apparent fungus growth in the wood, occasioning deterioration of the wood and threatening the need for extensive reconstruction ofthe cooling towers dictated the need for some preservative treatment.

For reasons of his own, and independent of the present invention; the proprietor of the cooling tower system elected first to steam sterilize 12 of the 13 cells leaving the thirteenth as a reference cell or blank in order to determine the effectiveness of the treatment. Immediately subsequent to the said steam sterilization, 1 of the 12 sterilized cells was treated in the manner of the present invention.-

In the present operation, each cell represented a structure of which the outside gross dimensions were approximately 60 feet width, 40 feet height, and 28 feet depth. As is typical of industrial cooling tower cell construction, the structure had extensive open space within it, and interior walks and access ways for use by maintenance and operation personnel.

Before any procedures were begun, a steam pipe manifold was installed within the cell. The steam manifold system in each of the cells was composed essentially of a 6 inch main pipe, branching successively into small pipes and therefrom into the orifices wherefrom steam issued interior to the cell. Control valves were appropriately provided. The main pipe was equipped with a valved opening through which the pesticide formulation of the present invention could be introduced. After installation of the steam lines and manifold, the fan stack of the tower cell was covered with a tarpaulin and the entire cell was thereafter shrouded on all exposed surfaces with polyethylene sheet, rein-forced with small polycaprolactam fiber rope.

The steam was then introduced interior to the cell to steam sterilize it. This sterilization being no part of the present invention is not further discussed here; however, the same steam manifold and source of steam were thereafter at once, without interrupting the steam flow, employed in the present invention to distribute into the cell the emulsifiable preparation of microbiocidal pesticide substance employed. The shrouding was maintained during the treatment according to the present invention.

At various points throughout the interior of the cell, samples of wood (redwood) were placed for subsequent removal and analysis for pick-up of the employed antimicrobial substance.

In carrying out the pesticide distribution, making use of an available pump, fifty gallons of an emulsifiable antimicrobial preparation of the present invention was diluted with forty gallons of water to obtain ninety gallons. This was injected, by the use of a two horsepower electric gear pump, at the rate of approximately a half gallon per minute, (approximately four pounds per minute) into a metered steam flow which was running in the range of to pounds of steam per minute.

Steam flow with pesticide injection was continued at the indicated rate for three hours, with introduction of fifty gallons of emulsifiable preparation diluted to ninety gallons with water.

Before the indicated dilution with Water, each hundred parts of the employed antimicrobial substance in the present operation consisted of 30 parts 2,3,4,6-tetrachlorophenol of industrial purity, twenty parts of a commercial emulsifying agent of which the manufacturer does not dis close, and may not know, the exact chemical structure, but which is advertized as a mixture of sulfonate and nonionic substances; it is an unpatented substance in the form of a liquid, and upon chemical analysis appears to be a mixture of sodium salts of sulfated petroleum oils and ethylene oxide adducts of fatty acids and entirely conventional in composition, and is described in industrial literature as a versatile emulsifying agent for pesticide substances. Together with these substances, the antimicrobial substance contained fifty parts by weight of mixed solvent substance of generally aliphatic alcoholic nature, in which the said tetrachlorophenol and emulsifying agent were soluble, which had a molecular weight range of from about 30 to about 400 and which was incompletely volatile in steam at 400 F. Of the aliphatic alcoholic substances, those of higher molecular weight served as an anti-blooming agent. The resulting preparation was, before dilution, a clear, light brown liquid moderately more viscous than water and emulsifying as a liquid immediately and completely upon contact with water. The aqueous emulsion was of a generally creamy appearance.

The injection of the said emulsifiable pesticide concentrate mixture into the introduced steam was completed within the indicated period of three hours.

At the conclusion of the injection period, injection of the said emulsifiable mixture was discontinued and soon thereafter introduction of steam was discontinued.

The said shrouds and associated supporting and reinforcing structures were removed and as soon as ventilation permitted, the interior structure was inspected. It was noted that, throughout he cell, wood surfaces were uniformly coated with a milky emulsion. Visual inspection upon this basis established that all exposed wooden surfaces including bottom surfaces and surfaces accessible through only small interstices had been covered, the said pesticide steam aerosol reaching all portions of the cell.

The Wooden blocks placed variously within the cell were removed and analyzed in sections, and all were found to contain tetrachlorophenol in pesticidally effective amounts not only upon the surface but to varying depths of several millimeters within. The cooling tower cell was thereafter restored to its normal service, and subsequently served for an extended period of time essentially free from further deterioration through fungus invasion.

In the best method known to the inventors to ascertain the actual penetration achieved according to the present invention, representative redwood blocks were treated according to the present invention by the application of a steam aerosol containing tetrachlorophenol labeled with radioactive carbon-14. The radioactive tetrachlorophenol was diluted with industrial tetrachlorophenol to obtain a tetrachlorophenol having a desired specific radioactive level and to prepare an emulsifiable tetrachlorophenol preparation essentially similar to that described, foregoing. This was injected as a steam aerosol over a period of thirty minutes into a treating chamber within which were blocks of redwood. Orifice steam pressure was about two to five pounds per square inch gauge. All exposed surfaces of the redwood blocks were covered with the milky emulsion of tetrachlorophenol.

Using standard laboratory techniques, samples of the redwood were removed as microtome slices, of each of which the position and depth was noted. The slices were then assayed for radioactivity and the penetration of tetrachlorophenol thus ascertained. Surface slice concentrations were found to be the greatest, but at depths within the wood block, of either end or transverse grain, up to one-half inch, the tetrachlorophenol was present at levels of concentration biocidal to a broad spectrum of Wooddestroying organisms.

Other penetration tests employing tetrachlorophenol labeled with carbon-14 were carried out. It was found that penetration of the tetrachlorophenol to substantial depth was improved by having the wood thoroughly wet before treatment began. However, whether the wood at the beginning of treatment was wet or dry, and whether exposure was to transverse or end grain, biocidal concentrations of tetrachlorophenol were uniformly introduced to depths never less than 3 millimeters and frequently as great as millimeters.

In evaluating such penetration tests it is to be noted that the wood employed in these tests was of a high finish grade, having uniformly smooh surfaces, free from checks, cracks, incipient decay, and without the general surface featuring that typically results from exposure to weather and water.

Routine chemical analysis without use of radioactive carbon compounds established that penetration into weathered wood in industrial and outdoor exposure was substantially greater, in view of the greater porosity of the exposed wood.

A cooling tower was treated by spraying the exposed wood. The spray consisted essentially of an industrial product consisting mostly of higher polychlorinated phenols in which pentachlorophenol predominated. It was composited together with organic solvents and diluents therefor which liquefied the mixture of said phenols and increased their volume to an amount satisfactory for uniform spray application. The spray application was Q made with a mechanically driven power sprayer and the nozzles out of which the spray issued were directed by hand by skilled operators working within the cell to be treated. Application was uniformly made to run off, that is, to such amount that more being applied formed surface runnels and ran off.

Upon analysis of wood in depth beneath the surface, it is ascertained that penetration of the pentachlorophenol as determined by chlorine position was essentially not deeper than about one-half to one millimeter.

The performances in service of the steam aerosol treated tower and the spray treated tower were compared. It was ascertained that the cell treated according to the steam aerosol injection method of the present invention remained free of decay for an extended period of timeseveral monthsafter new decay was well established in the wood of the sprayed cell, in an untreated cell, and in a cell that was steam-sterilized only.

In procedures essentially similar to the foregoing except that wood is mechanically loaded into and treated within a retort constructed originally for pressure application of solvent preservative solutions, application of emulsified pentachlorophenol in steam aerosol form achieves uniform surface coating and valuable protectant penetration of the said phenol into the surface of the wood. By the use of narrow spacers to hold layers of the wood for treatment apart from one another with minimum occlusion of surfaces to be treated, there is effected a preservative treatment of the wood conferring upon it a high degree of resistance to fungal decay, termites, powder post beetles and other wood-destroying microorganisms and insects.

The treatment of wooden structures such as concrete forms, wooden buildings, and the like as well as of leather, and cellulosic substances other than wood is effected in essentially the same way. Usually the preservative treatment of flexible such substances as fabrics, fibers, ropes and the like will be carried out by the immersion of such materials in a bath of preservative of desired composition. However, if desired, the steam aerosol application of an emulsifiable pesticide preparation according to the present invention to such substance is highly effective. In general, penetration of loosely textured substances tends to be deeper than penetration of more dense substances such as wood.

The application of pesticides other than chlorinated phenols is carried out in identical procedures and with equally good results. Organic chemical substances not decomposed by exposure to the steam, soluble in a solvent, in which solution an emulsifying agent of the specified property can also be dissolved, is effectively distributed according to the present invention. Thus, the known herbicide 2,4-dichlorophenoxyacetic acid is distributed with essentially the same efiiciency and penetration as is a chlorinated phenol. Also, the insecticide DDT similarly is distributed with good uniformity and penetration. The halohydroendomethanoindene pesticides are similarly distributed. Also, phenol and cresol are well distributed. Volatility of the organic substance in steam is not requisite. Polyglycols and glycol ethers of boiling temperatures substantially above steam temperature are successfully distributed.

A representative and satisfactory broad spectrum pesticidal preparation adapted to be used in the best method now known to the inventors consists essentially of 30 percent by weight of industrially pure 2,3,4,6-tetrachlorophenol, five parts by weight of a petroleum oil distillate boiling at approximately 250 C., five parts by weight methylethyl ketone, 35 parts by weight of a mixture of ethanol and acetone, and 5 parts by weight tetrahydrofuran. To this mixture, which is in the form of a solution, is added a suflicient amount, typically 20 parts by weight, of emulsifying agent meeting the criteria previously defined. Representative such agents include the aromatic sulfonate oxide condensate blends such as various of the Agrimul Wetting agents; similarly preparations containing sulfated fatty acid esters such as certain of the Ahcowet emulsifiers, certain of the Antarate emulsifying agents, especially adapted in pesticide employment. Also, a blend of more than one such agent can be prepared in the emulsifiable mixture itself, employing as a sulfonate material an industrial emulsifying agent such as one of the Nacconal materials, and as non-ionic component, one of the Nalco emulsifying agents. While the choice of an optimum emulsifying agent to be employed in the present invention may vary somewhat according to the identity of the toxicant with which it is to be employed and other factors, good results are obtained when employing any industrial emulsifying agent of reasonably good quality meeting the specific requirements hereinbefore set forth.

The manner of injecting of the emulsifiable preparation into the current of moving steam is not critical but it is preferred to achieve prompt and uniform dispersion of the emulsifiable material in the steam current. This is best achieved by the introduction of the emulsifiable preparation by means of a central orifice concentric with the steam line. Those skilled in the pesticide art will recognize that the steam lines should maintain conditions such that the pesticide does not deposit upon the walls thereof, especially at points at which steam temperatures may have dropped somewhat with resulting condensation or partial condensation of pesticide components on manifold walls and the like. This difficulty has uniformly been avoided with little or no trouble by the simple expedient of introducing the emulsifiable pesticidal preparation into the steam line at a point as near as possible to its point of issue from the manifold.

While the best method presently in view requires that the application of the steam aerosol pesticide according to the present invention be carried out within a confined space, that is to say, under a protective cover, such cover i not essential or critical to the practice of the present invention. It is contemplated also to employ the present technique in unprotected and uncovered space provided only that the pesticide be delivered to its site of application in the steam aerosol form herein defined.

We claim:

1. Technique of distributing upon, with penetration into, a Water-insoluble fibrous substance susceptible of degradation through the vital processes of a living organism, of an organic residual pesticidal substance soluble, together with emulsifying agent, in an organic solvent, which comprises the steps of preparing a solution of pesticidal organic substance and of emulsifying agent together in organic solvent,

introducing the resulting solution into a flowing current of steam at such rate that the said steam substantially wholly entrains the said solution,

conveying the resulting steam to a locus to be treated, releasing the said steam near to the locus to be treated; the said emulsifying agent being characterized by being (a) essentially unreactive alone or with pesticide at a temperature from approximately room temperature to approximately steam temperature,

(b) not wholly volatile in steam at the employed temperature,

(c) forming a liquid colloidal emulsion of the pesticide when cosolutions thereof with said pesticide are dispersed in water.

2. Process of claim 1 wherein the locus to be treated is covered by a confining structure.

3. Process of claim 2, wherein the pesticide is a halophenol.

References Cited by the Examiner UNITED STATES PATENTS 2,750,323 6/ 1956 Schmitz-Hillebrecht l67-38.7 X 3,197,272 7/1965 Regutti 21-7 MORRIS O. WOLK, Primary Examiner.

F. W. BROWN, Assistant Examiner. 

1. TECHNIQUE OF DISTRIBUTING UPON, WITH PENETRATION INTO, A WATER-INSOLUBLE FIBROUS SUBSTANCE SUSCEPTIBLE OF DEGRADATION THROUGH THE VITAL PROCESSES OF A LIVING ORGAMISM, OF AN ORGANIC RESIDUAL PESTICIDAL SUBSTANCE SOLUBLE, TOGETHER WITH EMULSIFYING AGENT, IN AN ORGANIC SOLVENT, WHICH COMPRISES THE STEPS OF PREPARING A SOLUTION OF PESTICIDAL ORGANIC SUBSTANCE AND OF EMULSIFYING AGENT TOGETHER IN ORGANIC SOLVENT, INTRODUCING THE RESULTING SOLUTION INTO A FLOWING CURRENT OF STEAM AT SUCH RATE THAT THE SAID STEAM SUBSTANTIALLY WHOLLY ENTRAINS THE SAID SOLUTION, CONVEYING THE RESULTING STEAM TO A LOCUS TO BE TREATED, RELEASING THE SAID STEAM NEAR TO THE LOCUS TO BE TREATED; THE SAID EMULSIFYING GENT BEING CHARACTERIZED BY BEING (A) ESSENTIALLY UNREACTIVE ALONE OR WITH PESTICIDE AT A TEMPERATURE FROM APPROXIMATELY ROOM TEMPERATURE TO APPROXIMATELY STEAM TEMPERATURE, (B) NOT WHOLLY VOLATILE IN STEAM AT THE EMPLOYED TEMPERATURE, (C) FORMING A LIQUID COLLOIDAL EMULSION OF THE PESTICIDE WHEN COSOLUTIONS THEREOF WITH SAID PESTICIDE ARE DISPERSED IN WATER. 